In an API announcement post, Sarver finally made clear what third-party developers have known for months: The company does not want developers to make Twitter clients any longer.

Sure, you can make a Twitter analytics tool like Klout or a Twitter-integrated CRM platform like HootSuite. And the company loves it when startups like Instagram and Foursquare let their users plug in their Twitter accounts.

But if you're thinking about making an app that displays and sends tweets, Sarver and company suggest you think again. Especially if that app has a different look and feel or uses different terms than Twitter uses itself. In other words, Twitter wants devs to build apps that use Twitter, not Twitter apps.

So why is Twitter cracking down — at least verbally, for now — on apps that look like and function like but aren't Twitter?

Twitter's Official Position on Third-Party Apps

Sarver on stage at Twitter's developer conference, Chirp.

For some time now, developers have been asking Twitter for clarification on how they can avoid getting in Twitter's way when building services on Twitter's API. When Twitter decided to make "official" mobile and desktop apps in the spring of 2010, many third-party shops that had been using the API got burned badly; and nobody wants to repeat that performance.

What Sarver said to developers today was direct: If you don't want to get burned, don't build pure-play Twitter clients. And if your app displays and sends tweets, make sure it looks and feels like Twitter.

"Developers ask us if they should build client apps that mimic or reproduce the mainstream Twitter consumer client experience," he wrote.

"The answer is no."

Twitter expects that it will be most consumers' client — that means it wants to be the only app users interact with on mobile devices, personal computers, tablets, etc. And as of today, Twitter's official apps are used by 90% of Twitter's users.

However, Sarver noted, "If there are too many ways to use Twitter that are inconsistent with one another, we risk diffusing the user experience."

How important is it to consumers that tweets look like Twitter? Sarver argues that the average end user will tend to be "confused" by changing UIs across various apps. He maintains that not only the design but also the core functions need to be the same across all Twitter apps.

"For example," he writes, "a number of third-party consumer clients use their own versions of suggested users, trends, and other data streams, confusing users in our network even more."

Sarver says that users might be confused by terms such as "like" and "comment" rather than "favorite" and "reply." These distinctions may seem trivial to Twitter power users, but Twitter staffers say these little things mean a lot.

Twitter corporate communications staffer Jodi Olson wrote to us in a separate e-mail, "Our own research indicates that people get confused when the experience isn't consistent, so we're taking steps to ensure users can interact with Twitter the same way everywhere."

A more egregious issue has been several apps' violation of the Twitter API terms of service in ways that violate Twitter users' privacy. Of these transgressions, Sarver writes, "Twitter has to revoke literally hundreds of API tokens [and] apps a week as part of our trust and safety efforts in order to protect the user experience on our platform. "

On the other hand, Sarver gave a sort of whitelist of apps the company feels is using the API appropriately and in ways that make good business sense for both parties. Publisher apps like SocialFlow, curation apps like Sulia, real-time data apps like Klout, brand-focused apps like HootSuite, and "value-added" apps like Foursquare all got a hall pass.

But conspicuously missing from the list were clients such as TweetDeck, the UberSocial family (which includes UberTwitter and Twidroyd), DestroyTwitter, Plume (formerly Touiteur), PowerTwitter, TwitBird — all the apps that give consumer-level Twitter users a slightly different user experience without adding too many bells and whistles.

App Makers' Initial Backlash

Laura Fitton speaking at Chirp.

Understandably, not every third-party dev has been thrilled with Twitter's announcement. In an e-mail discussion with Laura "Pistachio" Fitton, founder of Twitter app marketplace OneForty, Fitton took the side of the 750,000 apps that make up the Twitter ecosystem.

"Twitter is full of genuinely earnestly awesome people who want to do the right thing," she wirtes, "but it has resolutely failed to create the conditions for real business success on their platform."

When it comes to business success, Twitter responds that the kinds of apps it censured today aren't the kind that would be most likely to turn a profit, anyhow.

"We outlined what we see as the top five categories of business opportunities for developers," wrote Olson, "and explained that we do not think that building mainstream consumer third-party clients is one of them."

As for the different UIs between official and non-official Twitter apps, Fitton objects to Sarver's rationale. "There's enough confusion just switching between the various [official] Twitter apps — they all have UI inconsistencies.

"This argument was not at all convincing."

On the one hand, we've seen users flip out and come to some pretty daft conclusions over relatively minor UI changes. Then again, if users like one Twitter "skin," should they really be forced to give it up just because other users are "confused" by its knobs and buttons?

How Third-Party Apps Can Still Succeed

Identi.ca founder Evan Prodromou and Loic Le Meur at Chirp.

We spoke on the phone with Loic LeMeur, founder of Seesmic. During the Chirp debacle, when many app developers felt similarly betrayed, LeMeur spoke with a positive message that devs could still find success by creating diverse and valuable services that included but did not solely rely on Twitter's API.

His main message to third-party devs today was simple and common-sense: Communicate, cooperate and adapt.

"There are two types of Twitter apps," he said, "the ones Twitter likes and the ones that are competitive and don't have good communication with them.

"We've been talking almost daily with Twitter... We've been very open with our roadmap." While he says the startup never directly asked Seesmic to make any changes to the product, he said, "They know what we're building, and they have no concerns."

LeMeur notes that Seesmic has two factors that keep it out of Twitter's way: support for other services (such as LinkedIn and Facebook) and a focus on enterprise and professional users.

"Twitter can't do what we're doing; Twitter will never support Facebook pages. In that way, we don't compete at all," he said.

We discussed some of the apps that do aggressively compete with Twitter, which is an odd proposition in itself. Think about it: Why would you build an interface for another company's platform, then attempt to divert traffic and ad revenue to your interface, all while using the other company's underlying service?

"Competing with your number one partner is a little dangerous," said LeMeur, "and Twitter doesn't want that to happen."

How We Got Here & What Comes Next

Twitter co-founders Biz Stone and Evan Williams on stage at Chirp.

Back in 2007 when Twitter first opened up its API, the company was a model of what the social web was supposed to be — a collection of web services rather than websites — and its founders were lauded for their open approach to their own technology and evolving business model.

At the time, co-founder Biz Stone said, "The API has been arguably the most important, or maybe even inarguably, the most important thing we've done with Twitter. It has allowed us, first of all, to keep the service very simple and create a simple API so that developers can build on top of our infrastructure and come up with ideas that are way better than our ideas."

We've certainly come a long way since those days. Twitter has already adopted many of the ideas third-party devs brought into the system. For example, the impressive interface of the "New Twitter" felt more to us like a really great third-party app than anything else. And Twitter's mobile apps, which were a boon to overall Twitter usage, were informed and inspired by existing third-party apps, too.

But as the company continues to refine its product and search for its revenue, it's closing the door to apps that thrive on its API while stealing its traffic.

Even the most optimistic developers, folks like LeMeur, for example, have had to struggle to keep up with Twitter's shifting actions and attitudes. "I wasn't expecting such dramatic changes," said LeMeur, "but instead of complaining, I have to adapt to it."

While Twitter wouldn't comment on what might happen to some of these pure-play, competitive Twitter clients in the future, the company is a business, and its API is intended to help the business grow, not to make a charitable donation of Twitter's userbase and technology. It's fully conceivable that Twitter could revoke API access for apps like these in the future.

We'll be keeping an eye out for any possible fallout from Twitter's announcement today; in the meantime, take to the comments section to let us know how you feel about this situation.

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